1. Field of the Invention
The present invention relates to a phase-shift blankmask and a photomask, and more particularly to a phase-shift blankmask and a photomask which can achieve a fine pattern of not greater than 32 nm, preferably not greater than 14 nm, and more preferably not greater than 10 nm.
2. Discussion of Related Art
Today, as a need for a fine circuit pattern has been accompanied by high integration of large-scale integrated circuits (ICs), high semiconductor microfabrication process technology has emerged as a very important issue.
To this end, lithography technology has been developed up to a binary intensity blankmask, a phase-shift blankmask using a phase-shift film, a hardmask binary blankmask having a hard film and a light-shielding film, etc. so as to improve a resolution of a semiconductor circuit pattern. Such a blankmask is to fabricate a photomask with a high resolution and superior quality, and has been developed to get a finer pattern by making a film formed on a substrate thinner, controlling an etching speed of the film or the like method.
Among them, the phase-shift blankmask employs interference of light based on a predetermined phase difference (e.g., 170° to 190°) between exposure light passed through a transparent substrate and the exposure light passed through a phase-shifter, and has attracted attention as technology of forming a fine pattern for a semiconductor device since it can improve a resolution of a transfer pattern.
A conventional phase-shift blankmask has a structure where a phase-shift film, a light-shielding film having a light-shielding layer and an anti-reflective layer, and a resist film are stacked on a transparent substrate. The light-shielding film has a predetermined thickness to properly shield light and lower reflectivity, and the resist film is thick enough to serve as a mask in a process of etching the light-shielding film. As the resist film is thick, the resist film has a deviation in a critical dimension due to a loading effect while forming a pattern, thereby causing a defect in the pattern. Accordingly, there is a need of making the resist film thinner to effectively reduce the loading effect.
The thickness of the resist film is affected by the etching speed and thickness of the light-shielding film, and the resist film has relatively low etch selectivity under a dry etching condition for forming the pattern of the light-shielding film. Accordingly, the thickness of the light-shielding film has to be reduced in order to make the resist film thinner. However, a problem arises in that the reduced thickness of the light-shielding film cannot satisfy required optical properties, e.g., optical density, reflectivity, etc. Further, there has been proposed a method of adding oxygen (O) to a metal compound of the light-shielding film to increase the etching speed of the light-shielding film and thus make the resist film thinner. However, the light-shielding film containing oxygen (O) has a problem of increasing sheet resistance under a certain condition due to a composition ratio, a fabrication process, etc.